Fraud such as credit card fraud and identity fraud are common. To deal with fraud, enterprises such as merchants and banks use a variety of fraud detection systems. However, these fraud detection systems are susceptible to becoming obsolete within a short time because fraudsters change their methods of perpetrating fraud in order to maneuver past such fraud detection systems. A very common type of fraud is account take-over fraud. After a legitimate customer establishes a relationship with a merchant including one or more contacts by telephone, a fraudster takes over the account using information about the customer to impersonate the customer during additional contacts over the phone with the merchant. Unfortunately, even when the merchant detects that there has been a fraud, it can be difficult to determine which of multiple contacts originates from the fraudster.